What materials are used to produce forged wheels? Initially, steel was used for car wheels, and even now factory wheels are stamped from it. Titanium can also be used as a material. But for cast and forged wheels for several decades, alloy compositions have been used. For "forging" is most often taken so-called aircraft aluminum 6061, type AB, with additives of magnesium, copper, manganese and silicon. These additives allow to improve the strength characteristics of the finished products. Forged wheels from aluminum alloy have a number of advantages:
- Low weight.
- Resistance to corrosion.
- Neutrality to road and chemical reagents.
- Durability. Thanks to the fibrous structure of the material wheels do not burst and do not crack under severe impact or extremely low temperatures.
- Plasticity. This factor makes it possible to repair bent forged wheels by rolling on a machine.
Stages of production of forged wheelsIn fact, the epithet "forged" is very conditional, because they are produced by hot stamping in closed molds. In addition, even in the group of forged wheels have their own varieties of manufacturing technology. Conditionally, we can distinguish three varieties of finished products - monoblock, rolled and prefabricated. In the first case, the rim is a one-piece product made in a single process. In the second case, the rim rim is rolled out on a separate machine. In the third, the body and rim are stamped separately and only then assembled. Monoblock wheels are more common, so let's consider the stages of production of forged wheels on their example.
- Preparation of bolls. Aluminum bars are sent to the foundry, where the metal is melted and poured into cylindrical molds. The resulting castings, after cooling, are sawed into washers, which then go to the forging and pressing shop.
- Manufacturing of blanks ("pots"). Blanks are flattened under the press - "precipitate", then heated at a temperature of up to 430 ° C and molded in an intermediate die heated to 350 ° C. Its sectors lift the edges of the "pancake" and squeeze around, forming a part in the form of a pot with a protrusion at the bottom.
- Final stamping in the mold. The blanks are heated again and fed already to another die. An interesting fact is that no more than 11 seconds must elapse between heating and final stamping, otherwise the parts have time to cool down and lose the necessary degree of plasticity. One worker during this time has time to lubricate the hot die with grease, and two others have time to pick up the "pan" and transfer it to the mold. The upper part of the press is sharply lowered onto the die, the metal takes the specified shape, and its excess (flaking) is squeezed out. After lifting the press, the almost finished rim is taken out of the die.
- Hardening and artificial aging. For hardening parts are heated for several hours in a furnace at temperatures up to 515 ° C, making sure that the process went evenly, and then quickly immersed in water for cooling. During the stamping process, the structure of the metal changes greatly, turning from coarse-grained to fine-grained and fibrous. This creates internal mechanical stress, which in natural conditions takes 2-3 months to eliminate. Therefore, wheels are subjected to artificial aging: they are left in a furnace with a temperature of up to 160 ° C for 12-14 hours, and then let slowly cool down.
- Control. In the course of operation, wheels have to withstand serious loads, the safety of drivers and passengers depends on the quality of parts. Therefore, about 10% of wheels from one batch are subjected to control tests. For this purpose, their surfaces are etched to detect defects in stamping. One of the wheels is sawn and a fragment is cut out to study alloy homogeneity, specifics of deformation and heat treatment. In addition, the products are tested for strength, hardness, yield strength and relative elongation. If there is a discrepancy in at least one tolerance, another rim from the same batch is tested. If defects are detected in this rim, the whole batch is rejected. And if all indicators are normal, the wheels are sent for final machining.
- Turning and milling. On lathes from the wheels remove the remains of chips, in the hub part drill out the mounting holes, and in the rim - nipple hole. The parts are then sent to CNC milling machines to cut out the specified design. This can be either a standard pattern, without special frills, or a complex design with openwork spokes.
- Locksmithing. Sharp edges are removed and ground, some models of wheels are additionally polished to a mirror shine.
- Final inspection. Finished products are checked for compliance of the actual dimensions to the drawing, imbalance and runout of the rim.
Types of forged wheel finishesThe method of production and requirements for the performance characteristics of forged rims somewhat limit the design of wheels, but still retain the possibility of improving the appearance of products with additional processing. We can distinguish the following types of finishing for forged wheels, which are most popular:
- Giving the spokes an unusual shape. Usually it is done on individual projects and significantly increases the cost of finished wheels, but the result is worth it. Aluminum alloys are strong enough and plastic, which allows you to make the spokes more openwork or thin.
- Coloring. Applying a paint coating will add not only aesthetics, but also allow you to create additional protection from moisture. The most common option is monocolor, but it is possible to use two or more colors, and usually these are contrasting tones.
- Anodizing. Creating an oxide film on the surface of the rim also gives a beautiful appearance, which is especially relevant for premium class cars.
- Polishing. The mirror-like surface of the rim looks very stylish. Of course, such wheels require careful attitude and more thorough care.
- Engraving. Perhaps, this is the most practical of all types of rim finishing. With the help of engraving you can put on the rim any graphic or artistic image, as well as inscriptions. At the same time, you will not have to be afraid of scratches or heavy soiling. Wheel with engraving all this will calmly survive.